That is the obvious mistake: Hungarian=Magyar
It is not a mistake. We say for "Hungary" – Mađarska and it is from Magyar. That is the same.
Magyars were only one ethnicity in multiethnical kingdom. They were not even the dominant ethnicity ( the leading ethnical element were the Germans, since the founding of a kingdom
I am not sure what are you speaking of. I am saying that Magyars created Hungary, that land had Vojvodina in it for centuries and centuries and then Serbs used their numbers and took Vojvodina from Hungary. Just like Sqiptars in Kosovo. Hungarians lost a lot of population in combat with Ottomans in that area and some have escaped in the hinterland just like it happened with Serbs in Kosovo. Germans started to rule when Austria took the "Pole" position against the Turks.
Well, I mean that in past centuries a Hungarian refered to many erhnicities, not just Magyar. This small trick ( Hungarian=Magyar) allow them to appropriate persons of Hungarian history with different ethnicity than Magyar.
And who fonded the Hungarian kingdom? You should study more about this topic. For starters, find out something about Kopány uprising after corronation of st. Stephan. Just a small hint: These wars I mentioned were refered in chronicles as "wars between Teutons and Magyars" and guess on wich side was fighting the first Hungarian king.
And that Germans were dominant since the begining of the kingdom is simply a fact. Just look at privileges they gained directlly from hungarian kings. For example, in trials only a testimony of another German was taken in account and many, many more. These privileges went so far, that many Hungarian kings had to take countermeasures to avoid ethnic tensions, like "Privilegium pro Slavis" – http://en.wikipedia.org/wiki/Privilegium_pro_Slavis – a privileges that grated ethnic rights for Slovaks in town Žilina.